Contents lists available at ScienceDirect Comparative Biochemistry and Physiology, Part C journal homepage: www.elsevier.com/locate/cbpc Isolation and structural elucidation of antifungal compounds from Ryudai gold (Curcuma longa) against Fusarium solani sensu lato isolated from American manatee Jesmin Akter a,b , Md. Zahorul Islam b,c , Kensaku Takara a,b , Md. Amzad Hossain a,b, ⁎ , Ayako Sano a,b a The United Graduate School of Agricultural Sciences, Kagoshima University, Kagoshima 890-0065, Japan b Faculty of Agriculture, University of the Ryukyus, Okinawa 903-0213, Japan c Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh ARTICLE INFO Keywords: Turmeric Fusarium solani sensu lato Antifungal compounds 1 H NMR 13 C NMR ABSTRACT In a previous study, we reported that Curcuma longa strain Ryudai gold (RD) showed antifungal activity against Fusarium solani sensu lato (FSSL) among the different species and varieties of turmeric. The present study focused on isolation, identification and structural elucidation of antifungal compounds in RD. The ethyl acetate (EtOAc) fraction was eluted with n-hexane and EtOAc with gradually increasing the concentration of EtOAc (n- hexane:EtOAc; 100:0; 80:20; 60:40, 40:60, 20:80 and 0:100). The antifungal compounds were isolated from the most effective fraction by using silica gel, TOYOPEARL® HW-40F column, and high-performance liquid chro- matography. Structural identification of the antifungal compounds was conducted using 1 H NMR, 13 C NMR, and liquid chromatography-tandem mass spectrometry. The MeOH extract of the rhizome of RD inhibited the growth of FSSL in a concentration-dependent manner. The EtOAc fraction of the MeOH extract of RD demonstrated the highest antifungal activity against FSSL. The purified antifungal compounds were turmeronol B (1), turmeronol A(2), (E)-α-atlantone (3), dihydrobisdemethoxycurcumin (4), demethoxycurcumin (5) and curcumin (6). These six compounds showed concentration-dependent antifungal activity against FSSL. The concentration required for 50% growth inhibition (IC 50 ) of the four isolates of FSSL ranged from 116 to172, 127 to 185, 88 to 109, 90 to 112, 74 to 80 and 63 to 68 μM/L for turmeronol B, turmeronol A, (E)-α-atlantone, dihydrobisdemethox- ycurcumin, demethoxycurcumin and curcumin, respectively. These results suggested that RD contained poten- tial antifungal compounds that could be useful to control FSSL. The isolated compounds of RD can be a good source of natural antifungal agents or the lead compounds for the development of new synthetic drugs. 1. Introduction Turmeric (Curcuma longa L.), (family: Zingiberaceae) is native to Southeast Asia and extensively used as a spice, food preservative, and coloring material. It has a variety of therapeutic uses such as anti- microbial, antifungal, insecticidal, anti-inflammatory, vasodilatory and antioxidant properties (Apisariyakul et al., 1995; Khattak et al., 2005; Akter et al., 2018a, 2018b). The main bioactive constituent of turmeric is curcumin which is widely used in traditional Indian medicine for the treatment of anorexia, hepatic diseases, cold, cough, and other dis- orders (Chin et al., 2013). Curcuma longa (C. longa) mediated bio- synthesized silver nanoparticles showed potent antibiofilm activity against gram-positive bacteria such as S. aureus and S. pneumoniae (Kamble and Shinde, 2018). The EtOAc extract of C. longa showed potent fungicidal activities against phytopathogenic fungi under greenhouse (Kim et al., 2003). Curcumin, demethoxycurcumin and bisdemethoxycurcumin derived from C. longa were found effective against plant pathogenic fungi Phomopsis obscurans and Phomopsis viti- cola (Radwan et al., 2014). A recent study isolated curdione, iso- curcumenol, curcumenol, curzerene, β-elemene, curcumin, germacrone and curcumol from C. longa and found effective against Fusarium gra- minearum via the inhibition of cell membrane ergosterol synthesis (Chen et al., 2018). Turmeric has been found effective for controlling the mycelial growth of Fusarium oxysporum (Singh et al., 2002). Lean and Mohamed (1999) reported that turmeric was more antimycotic and antioxidative than lemon-grass, betel leaves, clove, black pepper leaves and Garcinia atroviridis. Moreover, the increasing resistance to anti- fungal compounds and the reduced number of available drugs led us to search for therapeutic alternatives among plants. Plants are the pro- mising source for new natural antifungal drugs, even though they have https://doi.org/10.1016/j.cbpc.2019.02.011 Received 13 November 2018; Received in revised form 8 January 2019; Accepted 10 February 2019 ⁎ Corresponding author at: Subtropical Field Science Center, Faculty of Agriculture, University of the Ryukyus, Senbaru-1, Nishihara 903-0213, Japan. E-mail address: amzad@agr.u-ryukyu.ac.jp (Md. A. Hossain). Comparative Biochemistry and Physiology, Part C 219 (2019) 87–94 Available online 22 February 2019 1532-0456/ © 2019 Elsevier Inc. All rights reserved. T